As computing moves off the desktop into the hands of mobile users, it is becoming more important for mobile devices to be aware of the user's context. Important pieces of context include the user's location, activities, nearby people and devices, and mode of transportation, if any. This knowledge can in turn be used by mobile devices to display reminders, to configure themselves for use with other devices, and to behave in a way that is appropriate for the surrounding environment (e.g., turn off cell phone ringer) or subcontexts of the surrounding environment such as whether particular states or transitions among states are occurring within the environment.
One significant aspect of context concerns whether or not the user (and the device) is inside or outside of a building or structure. For example, knowledge of such information can be used to facilitate determining the user's location (e.g., in a building or structure, in a particular building or structure, or in one of a set of known buildings or structures) and the user's mode of transportation (e.g., in a bus, car or airplane). Such knowledge can also be used to conserve power on systems that do not provide useful services inside buildings or outside. For example, because GPS typically fails to operate inside because satellite signals are not available inside, determination of the likelihood that a user is inside can be used to turn off a GPS system or put the system into a mode where it probes for satellite signals periodically so as to conserve the batteries of the GPS system.
One way to make an inside/outside determination would be to use a digital map of building footprints along with knowledge of the user's location or recent location. However, for most buildings such a map does not exist. Additionally, location data is not necessarily available, especially inside a structure where GPS typically fails.
In view of the foregoing, there is an unmet need for an improved technique to glean information regarding such inside/outside context of a device and/or an individual.